title: Suppression of retinal neovascularization by erythropoietin siRNA in a mouse model of proliferative retinopathy.
abstract: OBJECTIVE
  Erythropoietin (EPO), an oxygen-regulated hormone stimulating erythrocyte production, was recently found to be critical for retinal angiogenesis. EPO mRNA expression levels in retina are highly elevated during the hypoxia-induced proliferation phase of retinopathy. The authors investigated the inhibition of retinal EPO mRNA expression with RNA interference as a potential strategy to suppress retinal neovascularization and to prevent proliferative retinopathy.
  
  
  METHODS
  The authors used a mouse model of oxygen-induced retinopathy. Retinal EPO and Epo receptor (EpoR) expression during retinopathy development were quantified with real-time RT-PCR in whole retina and on laser-captured retinal vessels and neuronal layers. Retinal hypoxia was assessed with an oxygen-sensitive hypoxyprobe. A small interference RNA (siRNA) targeting EPO or control negative siRNA was injected intravitreally at postnatal (P) day 12, P14, and P15 during the hypoxic phase, and the effect on neovascularization was evaluated in retinal flatmounts at P17.
  
  
  RESULTS
  Retinal EPO mRNA expression in total retina was suppressed during the initial phase of vessel loss in retinopathy and was significantly elevated during the hypoxia-induced proliferative phase in all three neuronal layers in the retina, corresponding to an increased level of retinal hypoxia. EpoR mRNA expression levels also increased during the second neovascular phase, specifically in hypoxia-induced neovascular vessels. Intravitreous injection of EPO siRNA effectively inhibited approximately 60% of retinal EPO mRNA expression and significantly suppressed retinal neovascularization by approximately 40%.
  
  
  CONCLUSIONS
  Inhibiting EPO mRNA expression with siRNA is effective in suppressing retinal neovascularization, suggesting EPO siRNA is a potentially useful pharmaceutical intervention for treating proliferative retinopathy.
authors.affiliation: Department of Ophthalmology, Children's Hospital Boston, Harvard Medical School, Boston, Massachusetts 02115, USA.
authors.forename: Jing
authors.initials: J
authors.lastname: Chen
authors.forename: Kip M
authors.initials: KM
authors.lastname: Connor
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Aderman
authors.forename: Keirnan L
authors.initials: KL
authors.lastname: Willett
authors.forename: Oskar P
authors.initials: OP
authors.lastname: Aspegren
authors.forename: Lois E H
authors.initials: LE
authors.lastname: Smith
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D004195:Disease Models, Animal; D004921:Erythropoietin / Q000235:genetics*; D019084:Fluorescent Antibody Technique, Indirect; D005786:Gene Expression Regulation / Q000187:drug effects*; D006801:Humans; D007231:Infant, Newborn; D007267:Injections; D051379:Mice; D018613:Microscopy, Confocal; D010100:Oxygen / Q000633:toxicity; D034622:RNA Interference; D012333:RNA, Messenger / Q000378:metabolism; D034741:RNA, Small Interfering / Q000494:pharmacology*; D017467:Receptors, Erythropoietin / Q000235:genetics; D015861:Retinal Neovascularization / Q000235:genetics / Q000473:pathology / Q000517:prevention & control*; D012171:Retinal Vessels / Q000187:drug effects / Q000473:pathology; D012178:Retinopathy of Prematurity / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014822:Vitreous Body
chemical_list: D012333:RNA, Messenger; D034741:RNA, Small Interfering; D017467:Receptors, Erythropoietin; D004921:Erythropoietin; D010100:Oxygen